The Octet Rule

Happy atoms have a full outer energy level of electrons. They rarely combine with other elements. Nonreactivity is why they are called noble or inert. Noble Gases: the happiest elements

An octet is 8 valence electrons  is associated with the stability of the noble gases (does not occur with He; He is stable with 2 valence electrons) Valence Electrons He 2 Ne 8 Ar 8 Kr 8 In order to achieve an octet, elements will form ions. Octet Rule

Metals want to be happy. Metals form cations  by losing their valence electrons  resemble the nearest noble gas  have fewer electrons than protons Group 1 metals ion 1+ Group 2 metals ion 2+ Group 3 metals ion 3+

Formation of a Sodium Ion, Na + Sodium achieves an octet by losing its one valence electron.

Charge of Sodium Ion, Na + With the loss of its valence electron, a sodium ion has a 1 + charge. Sodium atom Sodium ion 11p + 11e – 10e – 0 1 +

Formation of Magnesium Ion, Mg 2+ Magnesium achieves an octet by losing its two valence electrons.

Charge of Magnesium Ion, Mg 2+ With the loss of two valence electrons magnesium forms a positive ion with a 2 + charge. Mg atom Mg 2+ ion 12p + 12p + 12e – 10e – 0 2 +

Nonmetals want to be happy too. Nonmetals form anions  gain electrons  have more electrons than protons  form negatively charged ions with 3 –, 2 –, or 1 – charges

Formation of a Chloride Ion, Cl – Chlorine achieves an octet by adding an electron to its valence electrons.

Charge of a Chloride Ion, Cl –  By gaining one electron, the chloride ion has a – 1 charge. Chlorine atom Chloride ion 17p + 17p + 17e – 18e – 0 1 –